Method for removing material from semiconductor wafer and apparatus for performing the same

ABSTRACT

A pressure is maintained within a volume within which a semiconductor wafer resides at a pressure that is sufficient to maintain a liquid state of a precursor fluid to a non-Newtonian fluid. The precursor fluid is disposed proximate to a material to be removed from the semiconductor wafer while maintaining the precursor fluid in the liquid state. The pressure is reduced in the volume within which the semiconductor wafer resides such that the precursor fluid disposed on the wafer within the volume is transformed into the non-Newtonian fluid. An expansion of the precursor fluid and movement of the precursor fluid relative to the wafer during transformation into the non-Newtonian fluid causes the resulting non-Newtonian fluid to remove the material from the semiconductor wafer.

CLAIM OF PRIORITY

This application is a divisional application of U.S. patent applicationSer. No. 11/174,080, filed on Jun. 30, 2005, entitled “Method forRemoving Material from Semiconductor Wafer and Apparatus for Performingthe Same.” The above-identified patent application is incorporatedherein by reference in its entirety.

BACKGROUND

During semiconductor fabrication, integrated circuits are created on asemiconductor wafer (“wafer”) defined from a material such as silicon.To create the integrated circuits on the wafer, it is necessary tofabricate a large number (e.g., millions) of electronic devices such asresistors, diodes, capacitors, and transistors of various types.Fabrication of the electronic devices involves depositing, removing, andimplanting materials at precise locations on the wafer. A process calledphotolithography is commonly used to facilitate deposition, removal, andimplantation of materials at precise locations on the wafer.

In the photolithography process, a photoresist material is firstdeposited onto the wafer. The photoresist material is then exposed tolight filtered by a reticle. The reticle is generally a glass plate thatis patterned with exemplary feature geometries that block light frompassing through the reticle. After passing through the reticle, thelight contacts the surface of the photoresist material. The lightchanges the chemical composition of the exposed photoresist material.With a positive photoresist material, exposure to the light renders theexposed photoresist material insoluble in a developing solution.Conversely, with a negative photoresist material, exposure to the lightrenders the exposed photoresist material soluble in the developingsolution. After the exposure to the light, the soluble portions of thephotoresist material are removed, leaving a patterned photoresist layer.

The wafer is then processed to remove, deposit, or implant materials inthe wafer regions not covered by the patterned photoresist layer. Suchwafer processing often modifies the photoresist layer in such a way asto make removal of the photoresist more difficult. For example, in thecase of a plasma etch process, the outer layer of the photoresist istransformed into a hard crust that is significantly less reactive thatthe underlying photoresist. After the wafer processing, the patternedphotoresist layer, its debris, as well as other types of polymer debrisleft after plasma etching, need to be removed from the wafer in aprocess called photoresist stripping. It is important to completelyremove the photoresist and polymer material during the photoresiststripping process because such materials remaining on the wafer surfacemay cause defects in the integrated circuits. Also, the photoresiststripping process should be performed carefully to avoid chemicallymodifying or physically damaging underlying materials present on thewafer. A need exists for improvement in the photoresist strippingprocess such that more complete removal of the photoresist and polymermaterial can be achieved while inflicting less chemical modificationand/or damage to the underlying wafer materials.

SUMMARY

In one embodiment, a method is disclosed for removing material from asemiconductor wafer. The method includes an operation for maintaining apressure in a volume within which the semiconductor wafer resides to besufficient to maintain a liquid state of a precursor fluid to anon-Newtonian fluid. The method also includes an operation for disposingthe precursor fluid on the semiconductor wafer while maintaining theprecursor fluid in the liquid state. More specifically, the precursorfluid is disposed proximate to the material that is to be removed fromthe semiconductor wafer. The method further includes an operation forreducing the pressure in the volume within which the semiconductor waferresides. The reduction in pressure causes the precursor fluid totransform into the non-Newtonian fluid. An expansion of the precursorfluid during the transformation into the non-Newtonian fluid causes theresulting non-Newtonian fluid to remove the material from thesemiconductor wafer.

In another embodiment, a method is disclosed for removing photoresistand polymer material from a semiconductor wafer. The method includes anoperation for disposing a solution on a semiconductor wafer to remove abulk photoresist material. The solution penetrates through a photoresistmaterial to remove the bulk photoresist material while leaving aphotoresist crust. Following removal of the bulk photoresist material, aprecursor fluid to a non-Newtonian fluid is disposed on thesemiconductor wafer while being maintained in a liquid state. Also, theprecursor fluid is disposed to penetrate through the photoresist crustto vacant regions underlying the photoresist crust. The method furtherincludes an operation for reducing a pressure ambient to thesemiconductor wafer to transform the precursor fluid into thenon-Newtonian fluid. An expansion of the precursor fluid during thetransformation into the non-Newtonian fluid causes the resultingnon-Newtonian fluid to remove the photoresist crust and polymermaterial.

In another embodiment, an apparatus is disclosed for removing materialfrom a semiconductor wafer. The apparatus includes a chamber having afluid input connected thereto. The fluid input is configured to disposea precursor fluid to a non-Newtonian fluid on the semiconductor wafer tobe supported within the chamber. The apparatus also includes apressurization device configured to control a pressure within thechamber. The pressurization device is capable of controlling a pressurewithin the chamber to maintain the precursor fluid in a liquid statewhen being disposed on the semiconductor wafer. The apparatus furtherincludes a pressure release device configured to release a pressurewithin the chamber to a lower pressure environment. Release of thepressure within the chamber is sufficient to cause the precursor fluidto transform from the liquid state into the non-Newtonian fluid. Anexpansion of the precursor fluid during the transformation into thenon-Newtonian fluid is sufficient to cause the resulting non-Newtonianfluid to remove the material from the semiconductor wafer.

Other aspects and advantages of the invention will become more apparentfrom the following detailed description, taken in conjunction with theaccompanying drawings, illustrating by way of example the presentinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is an illustration depicting a semiconductor wafer having apatterned photoresist layer defined thereon;

FIG. 1B is an illustration depicting the semiconductor wafer andpatterned photoresist layer of FIG. 1A after having the plasma etchingprocess performed thereon;

FIG. 1C is an illustration depicting the semiconductor wafer,photoresist crust, and polymer material of FIG. 1B following removal ofthe bulk photoresist portion using a conventional wet strip chemistry;

FIG. 2 is an illustration showing a flowchart of a method for removingmaterial from a semiconductor wafer, in accordance with one embodimentof the present invention;

FIG. 3A is an illustration depicting the configuration of FIG. 1Cfollowing performance of operations 201 and 203 of the method of FIG. 2,in accordance with one embodiment of the present invention;

FIG. 3B is an illustration depicting the configuration of FIG. 3Afollowing the operation 205 of the method of FIG. 2, in accordance withone embodiment of the present invention;

FIG. 3C is an illustration depicting the semiconductor wafer following arinse and dry process to clean the removed photoresist crust, theremoved polymer material, and non-Newtonian fluid from the semiconductorwafer, in accordance with one embodiment of the present invention;

FIG. 4 is an illustration showing a flowchart of a method for removingphotoresist and polymer material from a semiconductor wafer, inaccordance with one embodiment of the present invention; and

FIG. 5 is an illustration showing a processing chamber within which themethod for removing material from the semiconductor wafer can beperformed, in accordance with one embodiment of the present invention.

DETAILED DESCRIPTION

In the following description, numerous specific details are set forth inorder to provide a thorough understanding of the present invention. Itwill be apparent, however, to one skilled in the art that the presentinvention may be practiced without some or all of these specificdetails. In other instances, well known process operations have not beendescribed in detail in order not to unnecessarily obscure the presentinvention.

FIG. 1A is an illustration depicting a semiconductor wafer 101 having apatterned photoresist layer 103 defined thereon. It should beappreciated that the semiconductor wafer 101 can include a buildup ofmany different materials in various geometric arrangements, depending onthe extent of semiconductor fabrication that has occurred thus far. Thepatterned photoresist layer 103 can be defined on the semiconductorwafer 101 using a common photolithography process. In the presentdiscussion, the patterned photoresist layer 103 serves as a mask toprotect covered portions of the semiconductor wafer 101 from a plasmaused in a plasma etching process. Thus, the patterned photoresist layer103 also defines a pattern that will be etched into the semiconductorwafer 101.

Some wafer processing operations, such as the plasma etching process ofthe present discussion, can transform a thickness of a patternedphotoresist layer that is exposed to the plasma into a photoresistcrust. FIG. 1B is an illustration depicting the semiconductor wafer 101and patterned photoresist layer 103 of FIG. 1A after having the plasmaetching process performed thereon. As shown in FIG. 1B, following theplasma etching process, the patterned photoresist layer 103 is definedby a bulk photoresist portion 103 a and a photoresist crust 103 b,wherein the bulk photoresist portion 103 a underlies the photoresistcrust 103 b.

The photoresist material defining the bulk photoresist portion 103 a isessentially the same as the photoresist material defining the patternedphotoresist layer 103 prior to performing the plasma etching process.However, the photoresist crust 103 b differs significantly from the bulkphotoresist portion 103 a. For example, in contrast to the bulkphotoresist portion 103 a, the photoresist crust 103 b is a more rigidand porous material that adheres tenaciously to the semiconductor wafer101 surface.

Additionally, the plasma etching process can leave a polymer material104 on the semiconductor wafer 101 surface. During the etching processthe polymer material 104 can be created by reaction of species withinthe plasma with by-products of the etching process. For example, thepolymer material 104 can be a fluorocarbon based material that includesspecies from the substrate.

Following the plasma etching process, it is necessary to completelyremove the bulk photoresist portion 103 a, the photoresist crust 103 b,and the polymer material 104. Additionally, the photoresist and polymermaterials should be removed without causing chemical or physical damageto the underling features of the semiconductor wafer 101. One method forremoving the bulk photoresist portion 103 a involves performing a wetstripping operation. In the wet stripping operation, a wet stripchemistry is disposed over the semiconductor wafer 101 and photoresistmaterials. The wet strip chemistry is designed to penetrate through theporous photoresist crust 103 a and remove the bulk photoresist portion103 a through a dissolution process. Some example wet strip chemistriesinclude AP902 produced by ATMI, Inc. and EZStrip 523 produced by AirProducts and Chemicals, Inc., among others. Many of the conventional wetstrip chemistries are tetra ethylammonium hydroxide (TMAH) basedsolutions that are designed to provide rapid removal of the bulkphotoresist portion 103 a while remaining benign to underlying featuresof the semiconductor wafer 101.

However, those skilled in the art will appreciate that whileconventional wet strip chemistries are effective at removing the bulkphotoresist portion 103 a, the conventional wet strip chemistries arenot capable of effectively removing the photoresist crust 103 b withoutcausing damage to the underlying features of the semiconductor wafer101. Thus, conventional wet strip chemistries that are touted as beingcapable of removing the photoresist crust 103 b are so aggressive thatthey cause damage to the underlying features of the semiconductor wafer101.

FIG. 1C is an illustration depicting the semiconductor wafer 101,photoresist crust 103 b, and polymer material 104 of FIG. 1B followingremoval of the bulk photoresist portion 103 a using a conventional wetstrip chemistry. Due to the conventional wet strip chemistry beingcapable of removing the bulk photoresist portion 103 a but not thephotoresist crust 103 b, the photoresist crust 103 b remains attached tothe semiconductor wafer 101 following the conventional wet stripprocess. It should be appreciated that due to the porous nature of thephotoresist crust 103 b, the conventional wet chemistry process iscapable of penetrating through the photoresist crust 103 b and removingthe bulk photoresist portion 103 a that underlies the photoresist crust103 b. Consequently, following the conventional wet strip process, ashell of photoresist crust 103 b remains attached to each feature of thesemiconductor wafer 101. Additionally, due to the chemicalcharacteristics of the photoresist crust 103 b, a tenacious bond existsbetween the photoresist crust 103 b and the semiconductor wafer 101 atthe interfaces 105 therebetween. Therefore, a method is needed to removethe photoresist crust 103 b and polymer material 104 without damagingthe underlying semiconductor wafer 101.

FIG. 2 is an illustration showing a flowchart of a method for removingmaterial from a semiconductor wafer, in accordance with one embodimentof the present invention. The method includes an operation 201 formaintaining a pressure within a volume within which a semiconductorwafer resides to be sufficient to maintain a precursor fluid to anon-Newtonian fluid in a liquid state. In one embodiment, the volume ispressurized to greater than one atmosphere (1 atm) to maintain theprecursor fluid in the liquid state. In another embodiment, theprecursor fluid is formulated to be maintained in the liquid state atatmospheric (1 atm) pressure within the volume. In yet anotherembodiment, the precursor fluid is formulated to be maintained in theliquid state at a volume internal pressure less than one atmosphere (1atm). The precursor fluid is described in more detail below. The methodthen proceeds with an operation 203 for disposing the precursor fluid onthe semiconductor wafer while maintaining the precursor fluid in theliquid state. It should be understood that the precursor fluid in theliquid state is capable of being disposed within vias and betweenadjacent high-aspect ratio features defined on the semiconductor wafer.Additionally, the precursor fluid in the liquid state is capable ofpenetrating through the porous photoresist crust to reach vacant regionsthat may underlie the photoresist crust. Therefore, when the precursorfluid is disposed on the semiconductor wafer in the operation 203, theprecursor fluid is disposed proximate to material that is to be removedfrom the semiconductor wafer. Examples of such materials to be removedfrom the semiconductor wafer can include photoresist, photoresist crust,polymer material, and essentially any other unwanted residual material.

Following the operation 203, the method proceeds with an operation 205in which the pressure in the volume within which the semiconductor waferresides is reduced to cause the precursor fluid to transform into thenon-Newtonian fluid. A non-Newtonian fluid is a fluid in which theviscosity changes with the applied shear force. An example of anon-Newtonian fluid is a soft, condensed matter which occupies a middleground between the extremes of a solid and a liquid, wherein the softcondensed matter is easily deformed by external stresses. Foam is oneexample of a non-Newtonian fluid, as referenced herein, wherein gasbubbles are defined within a liquid matrix. It should be appreciated,however, that the non-Newtonian fluid associated with the presentinvention is not limited to a particular type of foam.

A volume expansion of the precursor fluid during its transformation intothe non-Newtonian fluid causes the resulting non-Newtonian fluid toremove the unwanted materials, e.g., photoresist crust, polymermaterial, etc., from the semiconductor wafer. It should be appreciatedthat as the precursor fluid transforms into the non-Newtonian fluid,expansion of the precursor fluid to the non-Newtonian fluid and therelative motion of the non-Newtonian fluid with respect to thesubstrate, i.e., semiconductor wafer, causes the non-Newtonian fluid toapply a mechanical force against the photoresist crust and polymermaterial such that the photoresist crust and polymer material areremoved from the semiconductor wafer. Thus, the liquid to non-Newtonianfluid transformation of the precursor fluid present below and adjacentto the unwanted materials causes a mechanical removal of the unwantedmaterials from the semiconductor wafer.

Because the precursor fluid works its way uniformly into spaces betweenfeatures present on the semiconductor wafer, the transformation of theprecursor fluid into the non-Newtonian fluid with the accompanyingexpansion will exert substantially uniform hydrostatic pressure on eachside of the features present on the semiconductor wafer. Therefore, thenon-Newtonian fluid will not exert differential forces on semiconductorwafer features, thus avoiding damage to the features. Additionally, thenon-Newtonian fluid acts to entrain the materials that are removed fromthe semiconductor wafer. Therefore, the removed materials such asphotoresist crust and polymer material will not resettle on andre-adhere to the semiconductor wafer.

As discussed above, the precursor fluid has a liquid state whenmaintained above a particular pressure. When exposed to a low enoughpressure, the precursor fluid transforms into the non-Newtonian fluid.For discussion purposes, the particular pressure below which theprecursor fluid transforms into the non-Newtonian fluid is referred toas a transformation pressure of the precursor fluid. In one embodimentthe precursor fluid is defined as a liquid having a propellant includedtherein by one of a number of methods such as dissolution, mixing,emulsification, etc. When the pressure is lowered below thetransformation pressure, the propellant in the precursor fluid willexpand to transform the precursor fluid into the non-Newtonian fluid.

The propellant in the precursor fluid is defined to maintain a liquidstate above the transformation pressure and a gas state below thetransformation pressure. For example, in one embodiment, propane (C₃H₈)can be used as the propellant. However, it should be understood that inother embodiments the propellant material can be essentially anymaterial that satisfies the physical state requirements relative to thetransformation pressure and is chemically compatible with the precursorfluid, the semiconductor wafer, and the processingenvironment/structures. At a pressure above the transformation pressurethe propellant in the liquid state is added to the precursor fluid. Inone embodiment, an amount of propellant added to the precursor fluid iswithin a range extending from about 5% by weight to about 20% by weightof the precursor fluid following addition of the propellant therein. Thelargest amount of propellant that can be dissolved in the precursorfluid is generally limited by the solubility of the propellant (in theliquid state) in the precursor fluid.

In one embodiment of the present invention, the transformation of theprecursor fluid to the non-Newtonian is accomplished through a rapiddecompression from a pressure greater than the transformation pressureto a pressure lower than the transformation pressure. In one embodiment,the pressure ambient to the precursor fluid is reduced at a rate suchthat the precursor fluid in the liquid state is transformed into thenon-Newtonian fluid within a duration extending from about 0.01 secondto about 2 seconds. As used herein, the term “about” refers to beingwithin plus or minus twenty percent of a given value. In anotherembodiment, the pressure ambient to the precursor fluid is reduced at arate such that the precursor fluid in the liquid state is transformedinto the non-Newtonian fluid within a duration extending from about 0.05second to about 0.2 second. In yet another embodiment, the pressureambient to the precursor fluid is reduced at a rate such that theprecursor fluid in the liquid state is transformed into thenon-Newtonian fluid within a duration of about 0.01 second.

For the non-Newtonian fluid to exert a sufficient amount of force on thephotoresist crust and polymer material to cause their removal from thesemiconductor wafer, the volume ratio of the non-Newtonian fluid to theprecursor fluid should be sufficiently large. In one embodiment, thevolume of the non-Newtonian fluid following expansion of the propellantin the precursor fluid is within a range extending from about 2 times toabout 100 times the volume of the precursor fluid in the liquid state.In another embodiment, the volume of the non-Newtonian fluid followingexpansion of the propellant in the precursor fluid is within a rangeextending from about 5 times to about 20 times the volume of theprecursor fluid in the liquid state.

In one embodiment, the base precursor fluid, i.e., the non-propellantportion of the precursor fluid, is defined by adding various componentsto an amount of deionized water. For example, the base precursor fluidcan be formulated to include surfactants for reducing surface tensionand other additives capable of stabilizing bubbles that form duringtransformation of the precursor fluid into the non-Newtonian fluid.Examples of such additives can include fatty acids, cellulose, oils, andproteins, among others. The base precursor fluid can also includedetergents and/or soaps. Additionally, hydrotropes can be included inthe base precursor fluid to bind strongly to the surface of micelles,thus controlling the size of the micelles. Additives that are capable ofreducing the adhesion at the interface between the photoresist crust andthe semiconductor wafer can also be included in the base precursorfluid. In one embodiment, an amount of the wet strip chemistry used toremove the bulk photoresist can be added to the precursor fluid so thatresidual bulk photoresist can continue to be removed during the removalof the photoresist crust.

With reference to the method of FIG. 2, the ambient pressure relative tothe semiconductor wafer during operations 201 and 203 can be maintainedjust above the transformation pressure. However, during operations 201and 203, there is no specific limit on the ambient pressure from theprecursor fluid perspective. Additionally, in some embodiments thepropellant used in the precursor fluid may partially liquefy atpressures approaching the complete liquefication pressure of thepropellant. In these embodiments, the precursor fluid can be defined toinclude an amount of propellant that is less than the amount ofpropellant expected at full liquefication pressure. Thus, in theseembodiments, the ambient pressure relative to the semiconductor waferduring operations 201 and 203 can be maintained at a pressure less thanbut approaching the complete liquefication pressure of the propellant.

As the pressure is decreased below the transformation pressure and thepropellant in the precursor fluid changes from liquid state to gasstate, the propellant in the gas state will behave as an ideal gas.Thus, according to the ideal gas law (PV=nRT), the volume of thepropellant in the gas state can be influenced by the temperature of thepropellant in the gas state. At a given pressure, a higher gastemperature will reflect a correspondingly higher gas volume,vice-versa. It should also be appreciated that the pressure insidebubbles will be affected by the size of the bubbles and the surfacetension of the liquid between the bubbles. At a fixed ambient pressure,smaller sized bubbles will have higher inside pressures relative tolarger size bubbles. With an increased gas volume upon transition of thepropellant from the liquid state to the gas state, the resultingnon-Newtonian fluid will occupy an increased volume. Thus, the method ofFIG. 2 can also include an operation for controlling a temperature tocontrol the volume expansion of the precursor fluid during thetransformation from the liquid state into the non-Newtonian fluid. Itshould be appreciated that the temperature should be controlled withconsideration for preserving the chemistry of the precursor fluid.

FIG. 3A is an illustration depicting the configuration of FIG. 1Cfollowing performance of operations 201 and 203 of the method of FIG. 2,in accordance with one embodiment of the present invention. Aspreviously described a precursor fluid 301 in a liquid state is disposedon the semiconductor wafer 101. The precursor fluid 301 is disposedbetween features present on the semiconductor wafer 101. The precursorfluid 301 also penetrates through the porous photoresist crust 103 b toregions underlying the photoresist crust 103 b that were previouslyoccupied by the bulk photoresist portion 103 a. In one embodiment, thesemiconductor wafer 101 can be subjected to a rinse and dry procedureprior to performing the method of FIG. 2.

FIG. 3B is an illustration depicting the configuration of FIG. 3Afollowing the operation 205 of the method of FIG. 2, in accordance withone embodiment of the present invention. As previously discussed, in theoperation 205, the pressure is reduced below the transformationpressure, thereby transforming the precursor fluid 301 into thenon-Newtonian fluid 303. The fluid expansion and fluid motion associatedwith the transformation of the precursor fluid 301 into thenon-Newtonian fluid 303 causes the non-Newtonian fluid to exertmechanical force on the photoresist crust 103 b and polymer material104, thereby removing the photoresist crust 103 b and polymer material104 from the semiconductor wafer 101. The removed photoresist crust 103b and polymer mate become entrained in the non-Newtonian fluid 303, suchthat removed photoresist crust 103 b and polymer material cannotresettle on and re-adhere to the semiconductor wafer 101. FIG. 3C is anillustration depicting the semiconductor wafer 101 following a rinse anddry process to clean the removed photoresist crust 103 b, the removedpolymer material 104, and non-Newtonian fluid 303 from the semiconductorwafer 101, in accordance with one embodiment of the present invention.

The method for removing photoresist crust from the semiconductor wafer,as previously described with respect to FIG. 2, can be incorporated aspart of a method for general removal of photoresist material from asemiconductor wafer. FIG. 4 is an illustration showing a flowchart of amethod for removing photoresist and polymer material from asemiconductor wafer, in accordance with one embodiment of the presentinvention. The method includes an operation 401 for disposing a solutionon the semiconductor wafer to remove a bulk photoresist material. Thedisposed solution is capable of penetrating through a photoresistmaterial to remove the bulk photoresist material while leaving aphotoresist crust.

Following removal of the bulk photoresist material, the method continueswith an operation 403 for disposing a precursor fluid to a non-Newtonianfluid on the semiconductor wafer. The precursor fluid of the presentmethod is equivalent to the precursor fluid previously discussed. Thus,the precursor fluid is maintained in a liquid state when disposed on thesemiconductor wafer. The precursor fluid is disposed to penetratethrough the photoresist crust to vacant regions underlying thephotoresist crust. Then, in an operation 405, a pressure ambient to thesemiconductor wafer is reduced to transform the precursor fluid into thenon-Newtonian fluid. A volume expansion of the precursor fluid duringthe transformation into the non-Newtonian fluid causes the non-Newtonianfluid to exert mechanical force on and remove the photoresist crust andpolymer material.

FIG. 5 is an illustration showing a processing chamber 501 within whichthe method for material from the semiconductor wafer can be performed aspreviously described, in accordance with one embodiment of the presentinvention. The chamber 501 is capable of maintaining a chamber internalpressure greater than the operating pressure at which the precursorfluid is maintained in the liquid state. A wafer support 503 is disposedwithin the chamber 501. The wafer support 503 is defined to hold asemiconductor wafer 505 during the material removal process.

The chamber 501 includes an input 507 connected to a precursor fluidsource 509. During operation, the precursor fluid is provided from theprecursor fluid source 509 through the input 507 to be disposed on thesemiconductor wafer 505, as indicated by arrow 511. The chamber 501 alsoincludes an input 513 connected to a pressurization device 515. Duringoperation, the pressurization device 515 is used to control the pressurewithin the chamber 501 through addition or removal of a processatmosphere gas, as indicated by arrow 517. The chamber 501 furtherincludes an input 531 connected to a temperature control 533. Duringoperation the temperature control 533 is capable of conditioning theprocess atmosphere gas via the input 531 to maintain a desiredtemperature within the chamber 501. Also, in one embodiment, thetemperature control 533 can be used to control a temperature of thewafer support 503 to in turn control a temperature of the semiconductorwafer 505.

A pressure release device 521 is connected to the chamber 501 through aconnection 519. During operation, the pressure release device 521 iscapable of rapidly releasing the pressure within the chamber 501, asindicated by arrow 523, to cause the precursor fluid to transform intothe non-Newtonian fluid on the semiconductor wafer 505 surface.Following the transformation of the precursor fluid into thenon-Newtonian fluid, the resulting non-Newtonian fluid and removedmaterials, e.g., photoresist and polymer material, can be removedthrough a connection 525 by a drain system 527, as indicated by arrow529. It should be appreciated that to avoid obscuring the presentinvention many additional details of the chamber 501 have not beendescribed herein. However, one skilled in the art will appreciated thatthe chamber 501 may include many features commonly associated withpressure chambers used for semiconductor wafer processing.

While this invention has been described in terms of several embodiments,it will be appreciated that those skilled in the art upon reading thepreceding specifications and studying the drawings will realize variousalterations, additions, permutations and equivalents thereof. Therefore,it is intended that the present invention includes all such alterations,additions, permutations, and equivalents as fall within the true spiritand scope of the invention.

What is claimed is:
 1. A system for removing material from asemiconductor wafer, comprising: a chamber; a precursor fluid to anon-Newtonian fluid, wherein the precursor fluid is a liquid having apropellant material in a liquid state, and wherein the non-Newtonianfluid has a viscosity that changes with an applied shear force, andwherein the precursor fluid includes one or more hydrotropes forcontrolling a size of micelles within the non-Newtonian fluid; a fluidinput connected to the chamber and configured to dispose the precursorfluid on a semiconductor wafer to be supported within the chamber; apressurization device configured to control a pressure within thechamber to maintain the precursor fluid in a liquid state when beingdisposed on the semiconductor wafer; and a pressure release deviceconfigured to release a pressure within the chamber to a lower pressureenvironment, wherein the release of the pressure within the chamber issufficient to cause the precursor fluid to transform from the liquidstate into the non-Newtonian fluid, whereby an expansion of theprecursor fluid during the transformation is sufficient to cause thenon-Newtonian fluid to remove material from the semiconductor wafer. 2.A system for removing material from a semiconductor wafer as recited inclaim 1, further comprising: a temperature control configured to controla temperature within the chamber, wherein control of the temperaturewithin the chamber enables control of the expansion of the precursorfluid during the transformation from the liquid state into thenon-Newtonian fluid.
 3. A system for removing material from asemiconductor wafer as recited in claim 1, wherein the pressure releasedevice is configured to release the pressure within the chamber to thelower pressure environment such that the precursor fluid is transformedfrom the liquid state into the non-Newtonian fluid within a durationextending from about 0.01 second to about 2 seconds.
 4. A system forremoving material from a semiconductor wafer as recited in claim 1,wherein the chamber is further defined to conduct a wet strippingoperation on the semiconductor wafer prior to disposing the precursorfluid on the semiconductor wafer, the wet stripping operation serving toremove a bulk portion of photoresist material from the semiconductorwafer while leaving a photoresist crust on the semiconductor wafer.
 5. Asystem for removing material from a semiconductor wafer as recited inclaim 1, wherein the precursor fluid is defined to penetrate throughphotoresist crust.
 6. A system for removing material from asemiconductor wafer as recited in claim 1, wherein the precursor fluidis defined such that the one or more hydrotropes bind to surfaces of themicelles.
 7. A system for removing material from a semiconductor wafer,comprising: a chamber defined to contain a semiconductor wafer andmaintain a controlled pressure in exposure to the semiconductor wafer,the chamber connected to a fluid input; a precursor fluid to anon-Newtonian fluid provided through the fluid input and in exposure tothe semiconductor wafer, wherein the precursor fluid is a liquid havinga propellant material in a liquid state, wherein the precursor fluidincludes one or more hydrotropes for controlling a size of micelleswithin the non-Newtonian fluid, and wherein the non-Newtonian fluid hasa viscosity that changes with an applied shear force; a pressure controldevice connected to the chamber to provide the controlled pressure inexposure to the semiconductor wafer such that the precursor fluid ismaintained in a liquid state when exposed to the semiconductor wafer;and a pressure release device defined to reduce the controlled pressurein exposure to the semiconductor wafer so as to cause the propellantmaterial in the precursor fluid to transform from the liquid state intoa gaseous state so as to cause the precursor fluid to transform into thenon-Newtonian fluid.
 8. A system for removing material from asemiconductor wafer as recited in claim 7, wherein the precursor fluidis defined such that the one or more hydrotropes bind to surfaces of themicelles.
 9. A system for removing material from a semiconductor waferas recited in claim 7, wherein the chamber is defined to cause theprecursor fluid to be applied in direct contact to the semiconductorwafer when the pressure control device provides the controlled pressurein exposure to the semiconductor wafer such that the precursor fluid ismaintained in the liquid state.
 10. A system for removing material froma semiconductor wafer as recited in claim 9, wherein the precursor fluidis defined to flow into vias and between high aspect ratio features onthe semiconductor wafer, the precursor fluid further defined topenetrate through a photoresist crust material present on thesemiconductor wafer to a region underlying the photoresist crustmaterial.
 11. A system for removing material from a semiconductor waferas recited in claim 7, wherein the precursor fluid includes an amount ofthe propellant material within a range extending from about 5% by weightto about 20% by weight.
 12. A system for removing material from asemiconductor wafer as recited in claim 7, wherein the precursor fluidincludes surfactants and additives capable of stabilizing bubbles thatform during transformation of the precursor fluid into the non-Newtonianfluid.
 13. A system for removing material from a semiconductor wafer asrecited in claim 7, wherein a volume of the non-Newtonian fluid iswithin a range extending from about 2 times to about 100 times thevolume of the precursor fluid in the liquid state.
 14. A system forremoving material from a semiconductor wafer as recited in claim 7,further comprising: a temperature control device defined to control atemperature of the precursor fluid in exposure to the semiconductorwafer so as to control the expansion of the precursor fluid during itstransformation from the liquid state into the non-Newtonian fluid.
 15. Asystem for removing material from a semiconductor wafer as recited inclaim 7, wherein the controlled pressure sufficient to maintain theprecursor fluid and propellant material in the liquid state is greaterthan 1 atmosphere (atm).
 16. A system for removing material from asemiconductor wafer as recited in claim 7, wherein the controlledpressure sufficient to maintain the precursor fluid and propellantmaterial in the liquid state is less than or equal to 1 atmosphere(atm).